Optical gyroscopes are important for inertial navigation. Optical gyroscopes are expected to play more important roles for applications where GPS is denied or compromised.
The Sagnac effect is directly related to optical gyroscopes. According to the Sagnac effect, the phase or frequency of light circulating in a loop geometry is modified by the rotation of the loop. The effect is manifested by a change in interference between the two counter propagating lights in the loop.
Optical gyroscopes can be broadly categorized into the interferometric type where the phase shift is measured, and the resonant type where a frequency shift due to rotation is measured. In both cases, the sensitivity of the gyroscope is linearly proportional to the length of the loop.
Chip-scale optical gyroscopes have been advanced to reduce the size of the device to adopt optical gyroscope technologies to other application areas. However, the optical propagation loss of typical waveguides is greater than 1 dB/m. This is several orders of magnitude inferior to optical fiber loss of about 0.2 dB/km. As a result, the loop length, and in turn the sensitivity, of the waveguide optical gyroscope is limited.